Re: netbsd-6: pagedaemon freeze when low on memory

[Lars Heidieker <lars%heidieker.de@localhost>]

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On 2013-03-06 09:05, David Laight wrote:
> On Tue, Mar 05, 2013 at 11:43:35PM -0600, David Young wrote:
>> Maybe we can avoid unnecessary locking or redundancy using a 
>> generation number?  Add a generation number to the vmem_t,
>> 
>> volatile uint64_t vm_gen;
>> 
>> Increase a vmem_t's generation number every time that
>> vmem_free(), vmem_xfree(), or vmem_backend_ready() is called:
> 
> Won't that generate a very hot cache line on a large smp system? 
> Maybe the associated structures are actually worse here! But
> per-cpu virtual address free lists might make sense.
> 

The quantum caches already do exacly this CPU local address caches.
Allocation that aren't cached by the quantum caches don't happen that
often. I like the idea of the generation counter, I see the
possibility for a race here that can be closed this way.

Lars


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Mystische Erklärungen:
Die mystischen Erklärungen gelten für tief;
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   -- Friedrich Nietzsche
   [ Die Fröhliche Wissenschaft Buch 3, 126 ]
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